Separately, a former group marketing manager for Windows Vista, Brian Marr, has left to become managing director at Seattle-based marketing agency Wexley School for Girls.

Marr, 31, oversaw viral marketing efforts for Windows Vista, including the elaborate Vanishing Point promotional game. He spoke highly of Microsoft Corp. and said he wanted to work in a leadership position at a smaller company. The difficult commute between Seattle and Redmond was a major factor, he said.

Microsoft has seen a number of high-profile executives and employees leave following Windows Vista's release. The departure of talented workers is a concern for any company, but it's also natural for employees to seek out new things after completing a big product such as Windows Vista, said Matt Rosoff, an analyst at research firm Directions on Microsoft in Kirkland.

"Microsoft is always going to have that tension as they get larger and larger," Rosoff said, calling it a fact of life at a large company. "There are always going to be some people who want to try something new, to go to a place where they will have an easier time making a splash."

Lam, 32, played a significant role in the design of features such as the Windows Vista "Start" button, Flip 3D window switching and screen savers. Lam, who had worked at Microsoft for six years, described her departure as amicable.

"It was difficult because I love the company a lot," she said of her decision. "I'm really proud of the work that the design team has done there together, especially in Vista. ... Vista was a really big accomplishment, and I was just looking for a change."

Cooperman, 38, who left Microsoft in November, described Lam as a "rock star" in the field. Cooperman and Lam worked together when he was a product unit manager overseeing Windows Vista's user interface.

Their new business partner, Smith, 39, is an experienced developer who worked at Microsoft for more than 10 years on programs including Internet Explorer and Windows and with Cooperman on a project called "Max" that took advantage of new Windows technologies.

Cooperman, who was at Microsoft for 10 years, said he didn't recruit his former colleagues. That would have run afoul of a provision in his Microsoft contract. He said the three simply had similar ideas about what they wanted to do.

"From my perspective, I'd always wanted to do something small and on my own," he said, adding that he still considers Microsoft a "fantastic place."

Cooperman declined to go into specifics but said Jackson Fish Market has a variety of different software projects in mind. The self-funded company, named after Cooperman's grandfather's store in Detroit, is currently consulting for a client that he declined to name.